Are Yoga’s Health Benefits Overblown?

WHY YOU SHOULD CARE

Because finding your bliss doesn’t always translate to fitness.

January 9, 2017

Mastering tree pose might boost your confidence and improve your Insta game. Not to mention your Tinder game, and maybe your dating life in general. But even if you step off the mat feeling blissed-out and #blessed, don’t be fooled. Recent studies on yoga’s fitness benefits are less uplifting than the high it can induce. In fact, they suggest that, for the most part, yoga falls short of national physical activity guidelines.

Most of us have heard this, even if we tune it out: The American College of Sports Medicine and the American Heart Association recommend 30 minutes of moderate-intensity physical activity five days a week to maintain health and reduce the risk of heart disease, which is the No. 1 killer of women. A systematic review found that hatha yoga is less intense than brisk walking. Indeed:

Yoga mostly counts as light-intensity exercise.

Again, that’s specific to the hatha type of yoga. D. Enette Larson-Meyer of the University of Wyoming conducted the review, which stemmed from her yoga-teacher-training final project. After reading in the bestseller The Science of Yoga: The Risks and the Rewards that yoga doesn’t burn much energy, she decided to do her own research on how specific poses and sequences measure up to national physical activity guidelines. She dug through 17 studies on intensity and calories burned in yoga, with a focus on hatha yoga, the most physically active style and the foundation for many other forms of yoga, including the oh-so-trendy Bikram practice.

The studies Larson-Meyer reviewed measured intensity using a unit known as MET, which indicates the number of calories an activity burns compared to the number of calories burned at rest. For instance, if you engage in an activity with an intensity of 4 METs, you would burn four times as many calories as you would lying on the floor doing nothing — which you may be happy to know also burns calories, at an intensity of 1 MET. The ACSM and AHA’s recommendation for moderate-intensity activity means they want you doing between 3 to 6 METs (again, that’s for 30 minutes, five days a week). Most of the yoga practices and specific poses Larson-Meyer evaluated fell below 3 METs, which classified them as light-intensity activity. That’s less intense than walking at a moderate pace on a solid, flat surface, which expends about 3.3 METs.

What about Bikram, the kind where room temperature averages a cool 105 degrees? Despite its rep as a calorie torch, Larson-Meyer’s review found that the heat didn’t really make much of a difference. In one study, the MET values of Bikram yoga still fell within the same range as those of yoga practiced at room temperature. Bikram yoga might feel more intense, since heat alters our mental perception of difficulty, and the Bikram series is challenging compared with many other forms of yoga, says Brian Tracy of Colorado State University, where he directs the Neuromuscular Function Laboratory. Also, heat increases our heart rate (and, for some of us, the likelihood of ralphing in down dog), to allow for more blood flow to the surface of the skin, where the heat can evaporate into the air, cooling the body. So while heart rate roughly indicates the number of calories burned at room temperature, “that’s not the case in heated exercise,” he says. To measure how Bikram yoga stacks up, though, researchers would need to compare subjects practicing the same sequence in a hot versus non-hot room.

To be sure, “it’s not all about the calories,” Tracy says. “Regular yoga or hot yoga has all these other benefits besides just the calorie burn.” Tracy and others have shown that yoga improves balance, strength and flexibility — crucial for people getting older — alleviates anxiety and lowers stress. Plus, it might offer a gentle form of activity for older adults or others who can’t engage in more intense exercise. Larson-Meyer adds that she reviewed only a small number of studies, mostly on healthy Indian men and American women in metropolitan cities, so the findings might not apply to everyone. Despite the estimated 36 million Americans who practice yoga, relatively few rigorous studies on yoga exist. Still, Tracy cites Larson-Meyer’s review, published in Medicine & Science in Sports & Exercise, as the “most comprehensive, most informative” summary of the research on yoga’s energy cost so far.

Certain poses and sequences did count as moderately intense, including the triangle, standing bow, standing head-to-knee and balancing stick poses. So did sun salutations, the vigorous, fast-paced set of movements practiced in many yoga classes, with some instructors guiding students through them for at least 10 minutes. In fact, a study of experienced Indian men and women who practiced four rounds of sun salutations at three minutes per round reported MET intensities in the vigorous range. In other words, “the whole practice isn’t going to be moderate or high-intensity, but certain components of it could be,” Larson-Meyer says.

Future research will hopefully investigate whether yoga helps with weight loss — not by burning calories, but by releasing hormonal signals that regulate appetite — and whether hot yoga releases different appetite regulators from non-hot yoga. So go ahead and get your downward dog on. While the calories might not show it, body and mind can still meet on the mat.